Prolific striker Alvaro Negredo join the club on a season-long loan from Valencia in the summer of 2016.
A Spanish international, who was a member of the Euro 2012 winning squad and averages almost a goal every other game for his country, brings a wealth of experience to Aitor Karanka's squad.
Negredo scored 23 goals in 48 appearances for Manchester City during his previous stint in England, a spell which prompted Valencia to pay in excess of £20m for his services during the summer of 2014.
The striker, who became the first Manchester City player to score a Champions League hat-trick, started his career with Real Madrid and has also had spells with Almeria and Sevilla.
Negredo scored his first Boro goal on his full debut against Stoke City - the club's first game back in the Premier League - in August 2016.